Postural hypotension is reported to be a frequent and significant clinical problem in the elderly. We hypothesize that this disorder is more common with increasing age because of age-associated changes in autonomic and adrenergic responses. There is very little information on the age-related changes in autonomic and adrenergic responses which occur immediately after standing. These upright changes are more relevant to the understanding of postural hypotension and may be very different from those age- related alterations described in the resting state. We also hypothesize that the blood pressure response to standing for subjects of any age will correlate with measurable differences in autonomic and adrenergic responses. Autonomic cardiovascular responses of healthy subjects aged 20-80+ will be examined. Blood will be collected in the supine position and after 5 minutes of upright posture for norepinephrine levels and blood cells. Platelets and lymphocytes will be assayed for alpha2- and beta2- adrenergic receptor number respectively, agonist affinity, and adenylate cyclase coupling. These results will be compared to the supine responses, correlated with the blood pressure response to standing, and the age associations identified.